1. Field of the Invention
This invention relates to phase inverters and, more particularly, to a microwave phase inverter.
2. Description of the Prior Art
The advantages of push-pull amplifier circuits, i.e., cancellation of even harmonics at the output, reduced susceptibility to power supply ripple voltages, etc., are well known. In the past few years, push-pull microwave field effect transistor amplifiers have been fabricated in a hybrid format. That is, individual transistors and capacitors were interconnected on a supporting substrate which contained metallization for interconnection at microwave frequencies. These circuits have typically used slot-microstrip tees to provide two input signals that are 180.degree. out-of-phase for the push-pull amplifier. One example of a push-pull power amplifier using slot lines is described in U.S. Pat. No. 4,097,814 which issued on June 27, 1978 to M. Cohn and is assigned to the assignee herein. Because the slot line tee employs .lambda./4 slot lines, it is relatively large and requires photoengraving and registration on both sides of the substrate, which is difficult to achieve in monolithic integrated circuits.
A split-load phase inverter as shown in FIG. 1 is a common circuit which is used at lower frequencies to provided phase inversion for push-pull amplifiers. The split-load phase inverter has two resistors, one coupled to the source and one coupled to the drain of a field effect transistor which are equal in value to provide equal output voltages which are 180.degree. out-of-phase. The gain of a split-load phase inverter approaches unity if the transconductance, g.sub.m times the value of the resistance R in ohms is much much greater than one.
It is therefore desirable to provide a monolithic microwave split-load phase inverter.
It is further desirable to provide a split-load phase inverter on a gallium arsenide substrate incorporating ion-implanted resistors.
It is further desirable to provide a monolithic microwave split-load phase inverter having a compensation network to balance the source-to-ground capacitance with the drain-to-ground capacitance at microwave frequencies.